The present invention in general relates to a discharge surface treatment device and a discharge surface treatment method. More particularly, this invention relates to a discharge surface treatment device for forming a modified layer on a metal surface by generating a discharge between an electrode composed of a modifying material or a material that is a source of the modifying material and metal that is a material to be surface-treated.
With respect to surface treatment techniques for coating a surface of metal with a modified layer having a corrosion resistant property and an abrasion resistant property, a discharge surface treatment method has been proposed in which: an electrode, composed of a modifying material or a material that is a source of a modifying material, and metal that is a treatment subject are put in a discharging process solution, and a discharge is generated in the discharging process solution between them so that a modified coat film, such as a hard coat film formed by the electrode material or a substance such as a metal carbide generated by a reaction of the electrode material through the discharging energy, is formed on a mold face through the discharged energy. The discharge surface treatment method of this type is known. See, for example, Japanese Patent Office Application Laid-Open Nos. 9-19829 and 9-192937.
In order to achieve the above-mentioned discharge surface treatment, it is necessary to apply current pulses between the electrode and the treatment subject member. With respect to the pulse voltage to be applied between the electrode and the treatment subject member, it is necessary to apply short pulses of 2 to 8 xcexcsec. so as to consume the electrode more easily, and also to provide a sufficient quiescent time of approximately 64 to 256 xcexcsec. between the pulses so as to prevent the treatment subject member from being processed due to the generation of a discharge between the electrodes; thus, the pulse discharging process using such current pulses makes it possible to form an appropriate coat layer on the treatment subject surface.
In a normal discharging process, in order to improve the processing rate with pulse energy per discharge being maintained constant so as to maintain surface roughness of a processed surface, it is desirable to make a quiescent time between the applied pulses as short as possible so as to discharge continuously at high speeds; however, in the above-mentioned discharge surface treatment, in order to prevent the treatment subject member from being processed by the discharging, it is necessary to provide a sufficient quiescent time between the pulses; therefore, there is a limitation in increasing the processing rate and improving the treatment speed by shortening the quiescent time of the applied pulses.
In other words, in the discharge surface treatment, it is impossible to simply shorten the pulse-to-pulse quiescent time, when the quiescent time is shortened in the discharge surface treatment, the discharging is concentrated, and the resulting heat damages the electrode, thereby failing to form a good coat film.
As described above, in order to provide a discharge surface treatment, it is necessary to properly consume the electrode by the discharging while carrying out the process at high speeds, and also to prevent the discharging from being concentrated, the pulse waveform that is applied between the electrodes is limited, and at present, there is a limitation in achieving a method for processing a great number of parts and for processing a large area with high efficiency.
With respect to methods for carrying out a discharge surface treatment efficiently on mass-production parts and a processing face covering a large area, for example, methods have been proposed in which a plurality of simple electrodes are simultaneously used so that a number of parts are simultaneously processed using the respective electrodes and in which a processing face covering a large face is divided into sections so that a number of electrodes are used so as to simultaneously process the respective sections.
However, even in the case when a plurality of electrodes are simply used, if the power-source unit is one, an independent discharging circuit is not formed for each electrode, with the result that a discharge between poles of each electrode is not performed independently in a separated manner. Therefore, in the same manner as the discharging treatment using one electrode, a discharge occurs only at a certain point that forms the minimum point of the distance between the poles among all the electrodes, and it is not possible to generate discharges simultaneously between the respective poles of a plurality of electrodes. For this reason, in the case when pulse conditions are maintained constant, from the viewpoint of the treatment efficiency, this case is the same as the case using only one electrode.
In the case when a column-shaped simple electrode is used, a discharge between the poles is always allowed to occur in the vicinity of the center of the electrode bottom face that is most susceptible to a discharge. Accordingly, on the treatment subject face opposing the electrode bottom face, formation of a modified layer successively progresses from the center of the opposing face in the same manner, and the formation of the treated film is complete when all the opposing face has covered with the film. Therefore, upon completion, the treated face has a raised state in the center. This becomes more conspicuous when an electrode having a large diameter and a large electrode bottom area is used. As a result, the uniformity of the modified layers is decreased.
The present invention has been devised to solve the above-mentioned problems, and its objective is to provide a discharge surface treatment device and a discharge surface treatment method for the device, which can carry out a discharge surface treatment uniformly with high efficiency at high speeds, and also can carry out a multi-layered, multiplex formation of modified layers having different functions, uniformly with high efficiency at high speeds.
The present invention provides a discharge surface treatment device for forming a modified layer on a metal surface by generating a discharge between an electrode composed of a modifying material or a material that is a source of the modifying material and metal that is a material to be surface-treated, wherein a plurality of electrodes, each of which is insulated from each other, are placed, each of the electrodes is connected to a power-source device exclusively used for the corresponding electrode so that each of the electrodes is supplied with a discharging pulse independently from the corresponding power-source device.
Therefore, pulse voltages are simultaneously applied between the respective electrodes and the respective treatment subject members by using power-source devices for the respective electrodes so that pulse discharges are independently generated simultaneously or virtually simultaneously between the respective electrodes and the respective surface treatment materials; thus, it becomes possible to improve the treatment efficiency without the necessity of alternating the quiescent time between pulses.
Moreover, the present invention makes it possible to provide a discharge surface treatment device in which electrodes composed of different materials can be used.
Therefore, it is possible to carry out a multi-layered, multiplex formation of modified layers with high treatment efficiency.
Moreover, the present invention makes it possible a discharge surface treatment device having an arrangement in which the treatment subject members are provided as race members of bearings and a plurality of electrodes are aligned in an extending direction of a ball rolling face of the race members.
Consequently, it is possible to carry out the discharge surface treatment of the ball-rolling face of the race members.
Moreover, the present invention makes it possible to provide a discharge surface treatment device having an arrangement in which the treatment subject members are provided as rails, and a plurality of electrodes are aligned in the length direction of the rails.
Therefore, it becomes possible to efficiently carry out a discharge surface treatment on long rails.
Moreover, the present invention also provides a discharge surface treatment method for forming a modified layer on a metal surface by generating a discharge between an electrode composed of a modifying material or a material that is a source of the modifying material and metal that is a material to be surface-treated, which has the steps of supplying discharging pulses independently from power-source devices, each exclusively used for the corresponding electrode of a plurality of electrodes that are insulated from each other, and generating discharges on the respective electrodes, thereby making it possible to improve the efficiency in the discharge surface treatment.
Therefore, pulse voltages are simultaneously applied between the respective electrodes and the respective treatment subject members by using power-source devices for the respective electrodes so that pulse discharges are independently generated simultaneously or virtually simultaneously between the respective electrodes and the respective surface treatment materials; thus, it becomes possible to improve the treatment efficiency without the necessity of alternating the quiescent time between pulses.
Moreover, the present invention makes it possible to provide a discharge surface treatment method in which electrodes composed of different materials can be used and a multi-layered, multiplex formation of modified layers is available.
Therefore, it is possible to carry out a multi-layered, multiplex formation of modified layers with high treatment efficiency.
Moreover, the present invention makes it possible to provide a discharge surface treatment method having an arrangement in which the treatment subject members are provided as race members of bearing and a plurality of electrodes are aligned in an extending direction of a ball-rolling face of the race members.
consequently, it is possible to carry out the discharge surface treatment of the ball-rolling face of the race members.
Moreover, the present invention makes it possible to provide a discharge surface treatment method having an arrangement in which the treatment subject members are provided as rails, and a plurality of electrodes are aligned in the length direction of the rails.
Therefore, it becomes possible to efficiently carry out a discharge surface treatment on long rails.